System and method for phase contrast imaging with improved efficiency

Abstract

A system and method is provided for magnetic resonance angiography (MRA) that includes performing a pulse sequence using the MRI system, the pulse sequence including a phase-based flow encoding to collect a time-series of image data from the portion of the vasculature of the subject and identifying at least a portion of the time series of image data corresponding to a period of reduced flow through the portion of the vasculature. The portion of the time series of image data is subtracted from the time series of image data to create a time series of images of the portion of the vasculature having background tissue surrounding the portion of the vasculature substantially suppressed.

The invention claimed is: 
     
       1. A method of acquiring a magnetic resonance angiography (MRA) image of a portion of a vasculature of a subject using a magnetic resonance imaging (MRI) system, the method comprising:
 performing a pulse sequence using the MRI system, the pulse sequence including a phase-based flow encoding to collect a time-series of image data from the portion of the vasculature of the subject; 
 monitoring, during the performing of the pulse sequence, a cardiac cycle of the subject and synchronizing the collection of the time-series of image data from the portion of the vasculature of the subject to the cardiac cycle of the subject; 
 identifying at least a portion of the time series of image data within the cardiac cycle and corresponding to a period of reduced flow through the portion of the vasculature; and 
 subtracting the portion of the time series of image data within the cardiac cycle from the time series of image data to create a time series of images of the portion of the vasculature having background tissue surrounding the portion of the vasculature substantially suppressed. 
 
     
     
       2. The method of  claim 1  wherein identifying at least a portion of the time series of image data includes selecting at least one image frame to create a subtraction image. 
     
     
       3. The method of  claim 2  wherein subtracting includes subtracting the subtraction image from each image frame reconstructed from the time series of image data. 
     
     
       4. The method of  claim 2  wherein identifying at least a portion of the time series of image data includes selecting multiple image frames and averaging the multiple image frames to create a subtraction image. 
     
     
       5. The method of  claim 4  wherein subtracting includes subtracting the subtraction image from each image frame reconstructed from the time series of image data. 
     
     
       6. The method of  claim 1  wherein identifying includes selecting at least one image frame from a time series of images reconstructed from the time series of image data corresponding to reduced flow from through the portion of the vasculature. 
     
     
       7. The method of  claim 1  wherein subtracting includes iteratively processing each image frame reconstructed from the time series of image data with respect to the identified at least a portion of the time series of image data. 
     
     
       8. The method of  claim 1  wherein a minority of image frames is acquired using a flow-rephased gradient waveform. 
     
     
       9. A magnetic resonance imaging (MRI) system comprising:
 a magnet system configured to generate a polarizing magnetic field about at least a portion of a subject arranged in the MRI system; 
 a plurality of gradient coils configured to apply a gradient field to the polarizing magnetic field; 
 a radio frequency (RF) system configured to apply an excitation field to the subject and acquire MR image data therefrom; 
 a computer system programmed to:
 perform a pulse sequence using the MRI system, the pulse sequence including a phase-based flow encoding to collect a time-series of image data from the portion of the vasculature of the subject; 
 monitor, during the performing of the pulse sequence, a cardiac cycle of the subject and synchronize the collection of the time-series of image data from the portion of the vasculature of the subject to the cardiac cycle of the subject; 
 identify at least a portion of the time series of image data within the cardiac cycle and corresponding to a period of reduced flow through the portion of the vasculature; and 
 subtract the portion of the time series of image data within the cardiac cycle from the time series of image data to create a time series of images of the portion of the vasculature having background tissue surrounding the portion of the vasculature substantially suppressed.